Waveform abnormality monitor

ABSTRACT

A portable, programmable electronic device for monitoring the heartbeat waveform of an ambulatory individual by sensing the difference between potentials from a pair of sensors attached to the individual, and electronically processing the waveform to detect and warn of the presence in that waveform of abnormalities, such as extrasystoles, which indicate the imminence of a possible heart attack. The potential difference, represented as a waveform formed by a series of R-wave complexes and any intermediate waveforms, is passed into a time controlled gate which is open during only the monitoring period following an R-wave complex so that an intermediate extrasystole will actuate an indicator.

United States Patent Michel [45] Oct. 24, 1972 [54] WAVEFORM ABNORMALITY3,132,208 5/1964 Dymski et a] ..128/2.05 S

MONITOR [72] Inventor: Walter A. Michel, 9035 North Primary Examinerwllham Kamm Mango Avenue, Morton Grove, Ill. Attorney-John Peele [57]ABSTRACT [22] Filed: Aug. 11, 1970 A bl bl l d f porta e, programma e eectronic evice or moni- [211 Appl- 62,831 toring the heartbeat waveformof an ambulatory in- [52] US. Cl. ..128/2.06 A from a pair of sensorsattached to the individual, and [51] Int. Cl. ..A6lb 5/04 electronicallyprocessing the waveform to detect and Field Of Searchv warn of thepresence in that waveform of abnormalil28/2.05 P, 2.05 R, 2- T ties,such as extrasystoles, which indicate the imminence of a possible heartattack. The potential dif- [56] References C' ference, represented as awaveform formed by a series UNITED STATES PATENTS of R-wave complexesand any intermediate waveforms, is passed into a time controlled gateWl'llCh T homton A is open during only the monitoring period followingan E R-wave complex so that an intermediate extrasystole ars t t an i dit 3,144,019 8/1964 Haber ..l28/2.06 A 3,533,402 10/ 1970 Siedband..128/2.06 A 8 Claims, 10 Drawing Figures 62 "IO 40 5 5'8 5 6o 64- 4 32W lou=i=ee Nee. (4V I IENTlhTR Cums: I HMPL J 82 i 86 4 36 HPID I GRTECUPPEK COUNT INO'TOR 78 dividual by sensing the difference betweenpotentials The invention relates to a compact programmable electronicdevice for recognizing some of the signs of a potential heart attack.Particularly, the device relates to an electronic device for sensingelectrical signals generated by the human body at selected points of thebody, which signals are related to the rate and constancy of the-heartbeat. The device further enables detecting variations from normalpatterns of the heart beat. When a pattern variation or abnormalityoccurs, the device, by an indicator, functions to warn the user of thepossibility of a heart attack. With the warning, the user can takeprecautions as necessary including medical consultation.

The risk of a heart attack is known to be greater in individuals whohave suffered an earlier heart attack as succeeding extrasystole occurscloser in time to the R- wave it follows. Thus, a selected time windowfollowing an R-wave can be looked at to cause a positive indi cationthat the dangerous class of extrasystoles are occurring.

It is an object of the present invention to provide a heart beatwaveform abnormality monitor having the aforegoing characteristics.

The above and other objects of the invention will be apparent from thefollowing detailed description, considered in connection with theaccompanying drawings compared to those who have not had a previousattack.

cal consultation and treatment, many of the complications due toventricular fibrillation can be prevented.

Although heart disease, such as ventricular fibrillation, developssuddenly in its dangerous form, it is generally preceeded by otherabnormalities in the pattern of the heart beat, which abnormalities, ifrecognized, can be used to warn the individual in due time.Abnormalities of the heart beat usually begin several hours before theactual heart attack. Hence, if the individual is warned, preventativemedical treatment ispossible.

Various types of electrocardiographic machines are known and areavailable at medical institutions for those individuals who can and willgo to the institution. However, the necessity for expert personnel tooperate these machines and to analyze the results makes the use of thesemachines relatively expensive and available only at fixed locations.Other machines and devices approaching portability have been suggestedin the prior art, but these have not provided complete and reliableportable electronic package usable by the ambulatory individual whowould desire to be warned, yet also desire minimum disruptions in dailylife due to periodic hooking up to an electronic package or frequentmedical consultation for analysis of the readings from the package.

The cardiac monitor of the present invention senses first a constant inthe form of the patients cardiac R- wave complex which is generally ofnormal duration although the frequency thereof may vary due to ordinarycauses. Using the QR rise of an R-wave complex as a starting point, themonitor examines the period between the initiating wave and a next wavefor the imminence of ventricular fibrillation which is evidenced byextrasystoles. These extrasystoles, caused by irritations of the heart,produce electrical pulsations longer or broader than the R-wave.Although extrasystoles occur irregularly between R-waves, the pattern ofoccurrences toward a dangerous condition can be recognized. That is,over an extended period of time, each in which like numerals refer tolike parts.

In the drawings: I

FIG. 1 is a block diagram of the major components of the monitor;

FIG. 2 is a block diagram of the computer logic circuit of the monitorof FIG. 1;

FIG. 3 is a block diagram of another embodiment of the computer logiccircuit of the monitor of FIG. 1; and

FIGS. 4a-4g are representations of various waveforms useful inexplaining the operation of the circuits of FIGS. 1 3.

Referring to FIG. 1, a schematic representation is shown of theelectronic components of the monitor of I the invention as attached toan individual or patient (not shown). A pair of transducing electrodesor sensors 12;, 14 of known construction are placed in contact with thepatient at two of the conventional points at which information forelectrocardiographic examinations may be taken. Since these severalrecognized points on the body generate potentials of differentparameters, this information is convertible by the electrodes intoelectrical signals, which when combined represent a heartbeat waveform.Several of the selected pairs of body points may be represented by thesum of other selected pairs. Thus, any one of the normally used pairsmay be selected although a preferred pair of points would provide apositive potential difference. In most individuals, such a preferredpoint pair would be the right arm and left leg, which pair will be usedfor the example in the present description.

As seen in FIG. 4a, the heart beat waveform comprises a series of R-wavecomplexes having P, Q, R, S, and T portions, according to conventionaldesignations. Further, a waveform may display abnormalities of the heartin a form such as an extrasystole 18 which appears normally between apair of R-wave complexes. The representation is shown with a pair ofnormal R- wave complexes 16 followed by an extrasystole l8 and anotherR-wave complex 16.

Electrodes 12, 14 are attached to the individual and are connected tothe heart beat waveform monitoring device 20 by leads 22, 24,respectively. The heart beat waveform signals are fed to a knownelectrocardiagraphic type differential amplifier 28 which combines thesignals into the series of R-wave complex waveforms. A high gainamplifier 32 receives and amplifies the R-wave complex and any signalsbetween a first and a succeeding R-wave complex. The amplified waveformis fed to a computer logic circuit 34 which looks for the presence ofabnormal waveform portions between a pair of R-wave complex waveforms,and upon detection of such a waveform portion actuates an indicator oralarm mechanism 36.

further amplifies the signal to a level acceptable by computer circuitry34, and feeds the signal along lead 42 to that circuitry. An output oractivating signal from computer circuitry 34 is fed along another lead44 to indicator 36. The above differential amplifier, the primaryamplifier, and any necessary intermediate buffer stages (not shown) arewell known to those skilled in the art and, thus, will not be describedin greater detail.

The novel computer logic circuitry shown generally at 34 is shown moreparticularly in FIG. 2. A monostable multivibrator 52 receives thesignal representative of the heartbeat waveform and triggers a blankingpulse preventing passage of other signals during the blanking period.The multivibrator is adjusted such that each QR rise of the R-wavecomplex initiates an on signal of the multivibrator. Multivibrator 52 isselected with values to cause triggering only when a predetermined valueis exceeded and to prevent being triggered by other segments of anR-wave complex, such as P and T waves, respectively. As represented inFIG. 4b, the on or blanking time of operation of multivibrator 52 isselected for predetermined periods adequate to prevent passage of the R,S, and T portions of the R- wave complex.

A differentiator or resistance capacitance network 56 is connected bylead 58 to multivibrator 52 to respond to the on" and off states of themultivibrator, and to differentiate these pulse signals shown in FIG.40. The resulting differentiated signal is passed along lead 60 to anegative clipper 62 which passes only positive pulse signals (FIG. 4d)along lead 64. The clipper presents a low impedance path to ground forall negative signals received, but passes the positive pulses to asecond monostable multivibrator 70.

Second multivibrator 70 is of construction similar to firstmultivibrator 52, and as shown in FIG. 4e, is adjustable .tovaryinglengths of on times following a trigger pulse. The multivibratorreceives any positive pulse passed by clipper 62, and turns on for apre-adjusted period. During the on time, the received pulse is fed alonglead 72 to an AND gate 74 to open same wherein any heart beat waveformoccurring during the on" time of multivibrator 70 and passed along lead78 from amplifier 32 may pass through the gate. No signal is received atAND gate 74 from an R-wave complex since the gate is blocked bymultivibrator 52. However, should an extrasystole appear while AND gate74 is in an on state, a pulse representative of the extrasystole willpass through the gate.

By a lead 82, a pulse representative of an extrasystole i is passed to aclipper 86 which is adjusted to exclude passing therefrom smallamplitude pulses due to extraneous signals or noise which might appearon lead 82.

Each pulse, passed by clipper 86 on lead 88, reaches pre-set counter 90which receives and stores that pulse for a predetermined time. Thecounter is selected and adjusted to accumulate a predetermined number ofpulses in a given time period before passing an indicator activatingpulse. Should the counter receive in the time period less than thenumber of pulses required to trigger same, an automatic reset circuittakes over to cause the counter to receive another sequence of pulseswithout triggering. However, assuming that counter 90 is set to triggerupon receiving one pulse, the trigger signal is passed along lead 44 toactivate alarm or indicator circuit 36. The alarm circuit may energizeany of several warning devices perceptible to a human sense. Hence, theindividual or patient is alerted only when an abnormality such as anextrasystole suggestive of an impending heart condition occurs.

As above described, second multivibrator is adjustable to maintain ANDgate 74 open for differing periods of time, preferably approximatelyhalf the period between consecutive R-wave complexes is selected.Assuming an extrasystole appears in the first half period after atriggering R-wave complex, indicator 36 will be activated as abovedescribed. However, if the extrasystole appears in the second halfperiod, first multivibrator 52 and second multivibrator 70 will receivethe representative signal as a synthetic R-wave complex. That is, sincein the second half period, multivibrator 52 and AND gate 80 are offawaiting another trigger level pulse. Thus, the circuits are availableto be triggered by a pulse analogous to a QR rise of an R-wave complex.Therefore, when such a pulse triggers the circuitry, AND gate 74 isturned on to receive the next R-wave complex which will cause counter torespond as though a true extrasystole had been received.

Referring to the modified embodiment of computer logic circuitry shownin FIG. 3, the heart beat waveform is monitored to detect anextrasystole by comparing presence of positive and negative overshootsof the extrasystole generated signals. As seen in FIG. 4a, theextrasystole has a definite negative overshoot not present in an R-wavecomplex of a normal waveform. Thus, by this embodiment, if anextrasystole is not in the waveform, indicator 36 would not beactivated.

As above described, a series of heart beat waveform signals is receivedby amplifier 32 and amplified for use by other circuitry. By thedescribed functions of first multivibrator 52, differentiator 56,negative clipper 62, and second multivibrator 70, a waveform other thanan R-wave complex is passed simultaneously on leads 72 and 78 andthrough AND gate 74.

Upon appearance of a pulse on lead 82 from AND gate 74, negative clipper86 removes the negative overshoot portion of the extrasystole and passesalong an output lead 88 only the positive portion of the waveform. Asignal stretcher or delay 92 receives the pulse from lead 88 andmodifies the time phase of that pulse before passing same to turn on asecond AND gate 94. As the amplifier passes signals along leads 72, 78,an unprocessed signal is fed along another lead 96 to a positive clipper98 which will pass only a negative signal such as the trailing portionof an extrasystole. A

signal inverter 102 receives the signal and changes its polarity to feedto AND gate 94 a signal of the same polarity as the signal from AND gate74. Since AND gate 94 is on at a time different from the negativesignal, delay 92 is necessary to bring the positive and invertednegative signal portions into time coincidence so as to simultaneouslyfeed both pulses to AND gate 94. When both pulses are received by ANDgate 94, an output signal is passed to counter 90 to activate indicator36 in the manner as above described.

The invention in its broader aspects is not to be limited to thespecific details shown and described, but may extend in details withinthe scope of the disclosure without departing from the scope of theinvention.

I claim as my invention:

1. Heart beat waveform monitoring apparatus for detecting by transducerssecured to a patient heart beat waveforms and for detecting heartbeatwaveforms occuring intermediate a pair of normal R-wave complexes of anelectrocardiagraphic heart beat waveform occuring during a predeterminedperiod comprising:

first means sensing presence of a QR rise in a heart beat waveform andtriggering at a predetermined.

level of said rise to generate a blanking pulse having a durationgreater than a normal R-wave complex;

second means producing a pulse of pre-set duration upon completion ofsaid blanking pulse from said first means;

an AND gate controlled to an on state by said pulse of said second meansto pass waveforms while in said on state;

third means accumulating waveform pulses occurring while said AND gateis periodically in said on state; and indicator means connected to beactivated upon receiving a pulse from said third means when said thirdmeans accumulates a predetermined number of waveform pulses in apredetermined period.

2. Apparatus as'in claim 1 wherein said'first sensing means is amultivibrator.

3. Apparatus as in claim 1 wherein said second means is amulti-vibrator.

4. Apparatus as in claim 1 wherein said third means is a counter.

5. Apparatus as in claim 1 wherein said third means includes a secondAND gate to receive a waveform simultaneously with said AND gate.

6. Apparatus as in claim 1 wherein said third means is a pulse counterresponsive to positive pulses passed by said AND gate.

7. Apparatus as in claim 6 including an input amplifier connected tosaid first means, said first AND gate, and said second AND gate toreceive waveforms.

8. Apparatus as in claim 1 including an input amplifier connected tosaid first means and said AND gate to receive waveforms, said AND gatepassing a waveform when in an on state.

1. Heart beat waveform monitoring apparatus for detecting by transducerssecured to a patient heart beat waveforms and for detecting heartbeatwaveforms occuring intermediate a pair of normal R-wave complexes of anelectrocardiagraphic heart beat waveform occuring during a predeterminedperiod comprising: first means sensing presence of a QR rise in a heartbeat waveform and triggering at a predetermined level of said rise togenerate a blanking pulse having a duration greater than a normal R-wavecomplex; second means producing a pulse of pre-set duration uponcompletion of said blanking pulse from said first means; an AND gatecontrolled to an ''''on'''' state by said pulse of said second means topass waveforms while in said ''''on'''' state; third means accumulatingwaveform pulses occurring while said AND gate is periodically in said''''on'''' state; and indicator means connected to be activated uponreceiving a pulse from said third means when said third meansaccumulates a predetermined number of waveform pulses in a predeterminedperiod.
 2. Apparatus as in claim 1 wherein said first sensing means is amultivibrator.
 3. Apparatus as in claim 1 wherein said second means is amulti-vibrator.
 4. Apparatus as in claim 1 wherein said third means is acounter.
 5. Apparatus as in claim 1 wherein said third means includes asecond AND gate to receive a waveform simultaneously with said AND gate.6. Apparatus as in claim 1 wherein said third means is a pulse counterresponsive to positive pulses passed by said AND gate.
 7. Apparatus asin claim 6 including an input amplifier connected to said first means,said first AND gate, and said second AND gate to receive waveforms. 8.Apparatus as in claim 1 including an input amplifier connected to saidfirst means and said AND gate to receive waveforms, said AND gatepassing a waveform when in an ''''on'''' state.